Generally, as the world's industries have developed and the population has swelled, resources, such as petroleum, coal, or natural gas, have been drained. Thus, much research on wind turbines, which generate power using wind force, have been conducted as an alternative energy source.
Meanwhile, a horizontal-type wind turbine, which has been widely used, is constructed so that a rotor having a plurality of vanes is provided on the upper end of a structure which is vertically erected on the ground. Such a horizontal-type wind turbine is operated as follows. That is, the rotor is rotated by wind force, and mechanical energy generated by the rotation of the rotor is transmitted to a power generator and converted into electrical energy, thus generating power.
However, in order to maintain stable power generating conditions, the rotor of the horizontal-type wind turbine must be positioned at a high level where a steady airflow exists. This causes the rotor support structure to become excessively high, thus incurring high installation costs, in addition to raising a risk of collapse. The height also causes many difficulties in maintaining and repairing the rotor, the power generator, and other components. Further, in view of the construction of the rotor, it is possible to generate power only when minimum wind velocity is 5-6 m/sec or more. Since the direction of the rotor must be manually adjusted according to wind direction, satisfactory power generation efficiency may not be expected in a place where wind is relatively weak and the direction of the wind frequently changes. Moreover, the wind turbine must stop operating so as to prevent components from being damaged in the event of a typhoon or gusting winds.
In order to solve these problems, an improved wind turbine is disclosed in Korean Patent Appln. No. 2004-0075991, which was filed by the applicant of the present invention. FIGS. 1 and 2 show the wind turbine. Referring to FIGS. 1 and 2, the wind turbine includes a rotary cylinder 20 installed to surround a support shaft 10. A plurality of wind vanes 30 is provided on the outer circumference of the rotary cylinder 20. Each of the wind vanes 30 is provided with a lattice comprising A plurality of horizontal and vertical bars. Rotating direction-adjusting blades 31 are provided on a surface of each wind vane 30 so as to open or close a predetermined number of holes of the lattices. In this case, when the lattice holes of wind vanes 30 provided to one side relative to the rotary cylinder 20 are closed by the rotation direction-adjusting vanes 31 and are subject to wind force, the lattice holes of wind vanes 30′ positioned at an opposite side are opened. However, this is problematic in that air resistance is generated due to the vertical and horizontal bars defining the lattices, so that a loss of energy is caused.